<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Promise 封装</title>
  </head>
  <body>
    <div class="container">
      <h2 class="page-header">Promise 封装 AJAX 操作</h2>
      <button class="btn btn-primary">点击发送</button>
    </div>
  </body>
  <script>
    //接口地址 http://api.apiopen.top/getJpke
    const btn = document.querySelector("#btn");
    //绑定单击事件
    btn.addEventListener("click", function () {
      //创建Promise
      const p = new Promise((resolve, reject) => {
        //1.创建对象
        const xhr = new XMLHttpRequest();
        //2.初始化
        xhr.open("GET", "http://api.apiopen.top/getJpke");
        //3.发送
        xhr.send();
        //4.处理响应结果
        xhr.onreadystatechange = function () {
          if (xhr.readyState === 4) {
            //判断响应状态码 2xx
            if (xhr.status >= 200 && xhr.status < 300) {
              //控制台输出响应体
              resolve(xhr.response);
            } else {
              //控制台输出响应状态码
              reject(xhr.status);
            }
          }
        };
      });

      //调用then
      p.then(
        (value) => {
          console.log(value);
        },
        (reason) => {
          console.warn(reason);
        }
      );
    });
  </script>
</html>
